There are three causes of Solar Heat Gain (SHG), namely, ultraviolet (UV) and infrared (IR) radiation and direct sunlight. Films have been successful in all but eliminating SHG due to UV and IR radiation. Problems remain in significantly reducing SHG due to direct sun light. To reduce the energy loss required to cool building interiors, some building codes have begun requiring a minimum SHG Coefficient (SHGC) of 0.40 in the windows, and/or the reduction of the size and/or amount of windows, especially on south facing facades, in an attempt to reduce the energy needed for cooling or counteracting the effects of SHG.
Currently, to reach these new standards of SHGC, windows, in addition to being insulated, are often either tinted, reflective, or both. Both of these solutions reduce light transmission through the window, and can reduce visibility, in a range from about 47% to as much as 90%, creating darker interiors, requiring artificial lighting, and, in a way, defeating the purpose and counteracting, at least to some extent, the savings realized in reduced energy cooling costs. This invention is intended to have minimal impact on visible light transmission, thereby reducing the need for interior lighting to counteract a reduction in visible light transmission, while still dramatically reducing SHG.
Architects have used obstruction designs (walls, overhangs, balconies, etc.) in an attempt to block the direct, heating rays of the sun. These solutions have limitations and they limit or block sight lines and views. Venetian blinds are also an attempt to create shading through obstruction, but they are ineffective in reducing SHG between the window and the blinds, causing radiant heat within the space.